Discharge lamp system and controlling method of the same

ABSTRACT

A discharge lamp system includes an AC power source, a rectifier, a power factor correction (PFC) circuit, a half-bridge circuit, and a controller. The AC power source provides an AC power. The rectifier converts the AC power into a DC power. The PFC circuit is electrically coupled to the rectifier and is configured for generating an output voltage. The half-bridge circuit is electrically coupled to the PFC circuit and a discharge lamp, and is configured for converting the output voltage into a voltage required by the discharge lamp. The controller is electrically coupled to the PFC circuit and the half-bridge circuit, and includes a timer for counting time, in which the controller controls the output voltage of the PFC circuit in accordance with a time period counted by the timer.

RELATED APPLICATIONS

This application claims priority to China Patent Application SerialNumber 201110201145.4, filed Jul. 18, 2011, which is herein incorporatedby reference.

BACKGROUND

1. Technical Field

The present disclosure relates generally to a discharge lamp system, andmore particularly to a discharge lamp system controlled by an outputvoltage of a power factor correction circuit and a controlling methodthereof.

2. Description of Related Art

Conventionally, high intensity discharge (HID) lamps have relativelyhigh efficiency, good color rendering, and a long service life, suchthat HID lamps are widely used in many applications.

Usually, in an HID lamp, a relatively low voltage of 220 V has to beincreased to a relatively high voltage rapidly by a ballast, in order toexcite a material in a quartz tube for radiating in arc. The highintensity white arc generated by the HID lamp resembles the sunlightduring the day. The HID lamp does not have a filament, and therefore, asituation in which a filament is broken to thereby render a lampinoperable will not occur. In addition, compared to a typical halogenlamp, the HID lamp not only has a longer service life but also hasimproved penetration, improved illumination and lower power consumptionfor saving electrical energy. Therefore, the HID lamp has been widelyresearched and developed with the aim of replacing conventional lightsources.

However, when the HID lamp is ignited, the relatively low voltage of 220V has to be increased rapidly to the relatively high voltage required bythe HID lamp. Therefore, the HID lamp cannot be operated alone. That is,a specific power supply circuit is necessary to enable the HID lamp tobe ignited and radiate light stably. The conventional power supplycircuit for the HID lamp includes a power factor correction (PFC)circuit and an inverter connected to the PFC circuit, where the invertercan be a full-bridge inverter or a half-bridge inverter. The half-bridgeinverter has the advantage of relatively low cost, and is thereforefrequently selected for use in the HID lamp. However, the HID lamp has aspecial characteristic. Namely a maximum voltage (i.e., open circuitvoltage, OCV) provided to the HID lamp by the half-bridge circuit isonly half of the output voltage of the PFC circuit. For example, if theoutput voltage of the PFC circuit is 400 V, the OCV of the half-bridgecircuit is thus 200 V, while the OCV required to ignite the HID lamp isusually in the range of about 250 V to 350 V. Thus, if the typicaloutput voltage of 400 V for the PFC circuit is used in combination withthe half-bridge inverter structure, problems will be encountered withrespect to the ignition of the HID lamp.

SUMMARY

One aspect of the present disclosure is to provide a discharge lampsystem including an AC power source, a rectifier, a power factorcorrection (PFC) circuit, and a half-bridge circuit. The AC power sourceis configured for providing an AC power. The rectifier is configured forconverting the AC power into a DC power. The PFC circuit is electricallycoupled to the rectifier, for generating an output voltage. Thehalf-bridge circuit is electrically coupled to the PFC circuit and adischarge lamp, for converting the output voltage into a voltagerequired by the discharge lamp. The controller is electrically coupledto the PFC circuit and the half-bridge circuit and includes a timer forcounting time, in which the controller is configured for controlling theoutput voltage of the PFC circuit in accordance with a time periodcounted by the timer.

According to one embodiment of the present disclosure, the controllerincludes a controlling unit, a first driver and a PFC controller. Thecontrolling unit includes the timer. The first driver is configured forgenerating a first driving signal. The PFC controller is electricallycoupled to the controlling unit and the first driver, for controllingthe PFC circuit by the first driver in accordance with the time periodcounted by the timer.

According to one embodiment of the present disclosure, when the timeperiod counted by the timer is less than or equal to a predeterminedtime, the PFC circuit outputs a first voltage, and when the time periodcounted by the timer is greater than the predetermined time, the PFCcircuit outputs a second voltage, in which the second voltage is lessthan the first voltage.

According to one embodiment of the present disclosure, the predeterminedtime is greater than or equal to a required time to ignite the dischargelamp.

According to one embodiment of the present disclosure, the dischargelamp system further includes an igniter activated when the time periodcounted by the timer is within the predetermined time and deactivatedwhen the time period counted by the timer extends past the predeterminedtime.

According to one embodiment of the present disclosure, the PFC circuitincludes a first switch, and the first driving signal is configured fordriving the first switch.

According to one embodiment of the present disclosure, the half-bridgecircuit includes a second switch and a third switch.

According to one embodiment of the present disclosure, the controllerfurther includes a second driver. The second driver is electricallycoupled to the controlling unit, for generating a second driving signaland a third driving signal, in which the second driving signal and thethird driving signal are configured for driving the second switch thethird switch, respectively.

According to one embodiment of the present disclosure, the dischargelamp is a high intensity discharge lamp.

According to one embodiment of the present disclosure, the first switch,the second switch, and the third switch are metal oxide semiconductorfield effect transistors (MOSFETs).

Another aspect of the present disclosure is to provide a controllingmethod for a discharge lamp system. The controlling method includesdetermining whether a time period counted by a timer is greater than apredetermined time. Next, a first voltage is outputted by a PFC circuitwhen the time period counted by the timer is not greater than thepredetermined time, and otherwise, a second voltage is outputted by thePFC circuit, where the second voltage is less than the first voltage.

According to one embodiment of the present disclosure, the predeterminedtime is greater than or equal to a required time to ignite a dischargelamp.

According to one embodiment of the present disclosure, an igniter isactivated when the time period counted by the timer is within thepredetermined time and deactivated when the time period counted by thetimer extends past the predetermined time.

Yet another aspect of the present disclosure is to provide a controllingmethod for a discharge lamp system. The controlling method includesdetermining whether a counted time period is within a time period T_(n),in which the time period T_(n) includes a first time period Δt_(n1) anda second time period Δt_(n2) following the first time period Δt_(n1),where n is an arbitrary positive integer from 1 to N, and N is aninteger greater than 1. Subsequently, a first predetermined voltageV_(n1) is outputted by a PFC circuit when the counted time period iswithin the first time period Δt_(n1). After that, a second predeterminedvoltage V_(n2) is outputted by the PFC circuit when the counted timeperiod is within the second time period Δt_(n2), where V_(n2)<V_(n1).

According to one embodiment of the present disclosure, the controllingmethod further includes outputting the second predetermined voltageV_(n2) by the PFC circuit when the counted time period is greater thantime t_(2n).

According to one embodiment of the present disclosure, the controllingmethod further includes outputting a third predetermined voltage V₃ bythe PFC circuit when the counted time period is less than time t₀.

According to one embodiment of the present disclosure, the controllingmethod further includes activating an igniter when the counted timeperiod is within the first time period Δt_(n1). Next, the igniter isdeactivated when the counted time period is within the second timeperiod Δt_(n2).

According to one embodiment of the present disclosure, the controllingmethod further includes outputting the first predetermined voltageV_(i1) by the PFC circuit when the counted time period is within thefirst time period Δt_(i1) of the time period T_(i). Next, the firstpredetermined voltage is outputted by the PFC circuit when the countedtime period is within the first time period Δt_(j1) of the time periodT_(j), where V_(i1)≠V_(j1), i and j are integers from 1 to N, and i≠j.According to one embodiment of the present disclosure, V_(i1) can beequal to V_(j1).

According to one embodiment of the present disclosure, the controllingmethod further includes outputting the second predetermined voltageV_(i2) by the PFC circuit when the counted time period is within thesecond time period Δt_(i2) of the time period T_(i). Next, the secondpredetermined voltage V_(j2) is outputted by the PFC circuit when thecounted time period is within the second time period Δt_(j2) of the timeperiod T_(j), where V_(i2)≠V_(j2), i and j are integers from 1 to N, andi≠j. According to one embodiment of the present disclosure, V_(i2) canbe equal to V_(j2).

The discharge lamp system and the controlling method thereof of thepresent disclosure are configured for controlling the output voltage ofthe PFC circuit rapidly according to the time period counted by thetimer, in order to control an open circuit voltage (OCV) of ahalf-bridge inverter, such that the required voltage to ignite thedischarge lamp and to operate the same stably is provided by thehalf-bridge inverter. Moreover, because a half-bridge topology isselected in the present disclosure, cost savings are realized.

It is to be understood that both the foregoing general description andthe following detailed description are by examples, and are intended toprovide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a discharge lamp system according to oneembodiment of the present disclosure.

FIG. 2 is a waveform diagram of an output voltage of a PFC circuit ofthe discharge lamp system according to one embodiment of the presentdisclosure.

FIG. 3 is a flow diagram of a controlling method for the discharge lampsystem in one embodiment of the present disclosure.

FIG. 4A and FIG. 4B are controlling sequences of the discharge lampsystem in one embodiment of the present disclosure.

FIG. 5 is a flow diagram of a controlling method for the controllingsequences shown in FIG. 4A.

DETAILED DESCRIPTION

Reference will now be made in detail to the present embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers are used in thedrawings and the description to refer to the same or like parts.

As used herein, “around,” “about” or “approximately” shall generallymean within 20 percent, preferably within 10 percent, and morepreferably within 5 percent of a given value or range. Numericalquantities given herein are approximate, meaning that the term “around,”“about” or “approximately” can be inferred if not expressly stated.

Referring to FIG. 1, a block diagram will be described that illustratesa discharge lamp system 100 according to one embodiment of the presentdisclosure. The discharge lamp system 100 includes a power source AC, anelectromagnetic interference filter (EMIF) 110, a rectifier 120, a powerfactor correction (PFC) circuit 130, a half-bridge circuit 140, adischarge lamp 150 and a controller 160, in which the discharge lamp 150can be a high intensity discharge (HID) lamp, and the power source ACcan be an alternating current power source. One side of the EMIF 110 isconnected to the power source AC, for filtering an interference signalto the power source AC. It is noted that the discharge lamp system 100can be configured without the EMIF 110 and its inclusion within thedischarge lamp system 100 as described herein is not intended to limitthe present disclosure.

One side of the rectifier 120 is connected to the other side of the EMIF110. The rectifier 120 is configured for converting the AC powerprovided by the power source AC into a DC power. The PFC circuit 130 isa boost PFC circuit including an inductor L1, a diode D1, and a firstmetal oxide semiconductor field effect transistor (MOSFET) S1 (alsoreferred to as a switch S1 herein). The PFC circuit 130 can beconfigured to perform a boost process to an input voltage of the PFCcircuit 130, such that an output voltage V is generated. It is notedthat other topologies can be selected for the PFC circuit 130, such as abulk-boost PFC circuit, and the topology described herein and shown inFIG. 1 is not intended to limit the present disclosure.

The half-bridge circuit 140, which may be, for example, a half-bridgeinverter, is connected to the PFC circuit 130, for converting the outputvoltage V provided by the PFC circuit 130 into a voltage required by thedischarge lamp 150. The half-bridge inverter 140 includes anelectrolytic capacitor C1, an electrolytic capacitor C2, an igniter1410, an inductor L2, a capacitor C3, a second MOSFET S2 (also referredto as a switch S2 herein), and a third MOSFET S3 (also referred to as aswitch S3 herein). The electrolytic capacitor C1 and the electrolyticcapacitor C2 are connected in series with each other. The igniter 1410is connected in series to the discharge lamp 150. The inductor L2 isconnected in series with the discharge lamp 150. The capacitor C3 isconnected in parallel with the discharge lamp 150.

The controller 160 can include a controlling unit 1610, a first driver1630, and a PFC controller 1620. The controlling unit 1610 includes atimer 1611. The first driver 1630 is configured for generating a firstdriving signal (S1 driving signal). The PFC controller 1620 is connectedto the controlling unit 1610 and the first driver 1630, for controllingthe PFC circuit 130 through the first driver 1630 in accordance with atime period counted by the timer 1611. Namely, the PFC controller 1620generates a controlling signal in accordance with the time periodcounted by the timer 1611, and transmits the controlling signal to thefirst driver 1630. Thus, the first driver 1630 outputs the first drivingsignal for driving the switch S1 of the PFC circuit 130, such that theoutput voltage of the PFC circuit 130 can be controlled. Moreover, thecontroller 160 further includes a second driver 1640 connected to thecontrolling unit 1610, and the second driver 1640 is configured forgenerating a second driving signal (S2 driving signal) and a thirddriving signal (S3 driving signal) to drive the switches S2 and S3 ofthe half-bridge inverter 140, respectively.

In one embodiment of the present disclosure, at first, a time period iscounted by the timer 1611 of the controlling unit 1610. The controllingunit 1610 then instructs the PFC controller 1620 to control the switchS1 through the first driver 1630 in accordance with the time periodcounted by the timer 1611, such that the output voltage of the PFCcircuit 130 can be controlled. When the counted time period is less thanor equal to a predetermined time, the PFC circuit 130 outputs a firstvoltage, and when the counted time period is greater than thepredetermined time, the PFC circuit 130 outputs a second voltage. Outputvoltage waveforms of the first voltage and the second voltage are shownin FIG. 2. FIG. 2 is a waveform diagram of the output voltage of the PFCcircuit 130 of the discharge lamp system 100 according to one embodimentof the present disclosure. The time period counted by the timer 1611 ist and the predetermined time is t₁. When t is less than or equal to t₁,the PFC circuit 130 outputs the first voltage V₁, and when t is greaterthan t₁, the PFC circuit 130 outputs the second voltage V₂.

It is noted that the predetermined time t₁ can be greater than or equalto a required time to ignite the discharge lamp 150. Moreover, when theboost topology is selected for the PFC circuit 130, the first voltage V₁outputted by the PFC circuit 130 is in the range of about 450 V to 550V. Preferably, the first voltage V₁ is 500 V. In addition, the secondvoltage V₂ outputted by the PFC circuit 130 is in the range of about 380V to 420 V. Preferably, the second voltage V₂ is 400 V.

Furthermore, when the bulk-boost topology, is selected for the PFCcircuit 130, the first voltage V₁ outputted by the PFC circuit 130 is inthe range of about 450 V to 550 V. Preferably, the first voltage V₁ is500 V. Additionally, the second voltage V₂ outputted by the PFC circuit130 is in the range of about 100 V to 420 V. Preferably, the secondvoltage V₂ is in the range of about 300 V to 400V.

Generally speaking, due to an operating characteristic of the dischargelamp, before, the discharge lamp is ignited, a high ignition voltage(usually several kilovolts (kV)) is needed in an igniting process toactivate the discharge lamp. Further, a relatively high open circuitvoltage (OCV) (usually several hundred volts) is needed to assist thedischarge lamp to change from a glow state into an arc state after thedischarge lamp is ignited. After the discharge lamp is ignited and isoperating stably, it is necessary only that an operating voltagesufficient to maintain a stable operating state of the discharge lamp issupplied.

In the present embodiment, the manner in which the output voltage of thePFC circuit 130 is changed can be selected so as to realize the requiredvoltage in the operation of the discharge lamp 150. The output voltageof the PFC circuit 130 can be increased to raise the open circuitvoltage of the half-bridge inverter 140 within a specific time period,and then the output voltage of the PFC 130 circuit can be decreased tolower the open circuit voltage of the half-bridge inverter 140 after thespecific time period. An igniting circuit can be operated during a timeperiod, in which the PFC circuit 130 outputs the first voltage (highvoltage); therefore the relatively high ignition voltage will begenerated. The igniter 1410 can stop the operation during the timeperiod, in which the PFC circuit 130 outputs the second voltage (lowvoltage); therefore the relatively high ignition voltage will not begenerated. Thus, an exhaust of the discharge lamp 150 can be decreasedin order to improve the service life of the discharge lamp 150. The PFCcircuit 130 outputs the relatively low voltage after the discharge lamp150 is operated in a stable condition, such that the efficiency of thewhole discharge lamp system 100 can be improved.

Referring to FIG. 3, a flow diagram will be described that illustrates acontrolling method for the discharge lamp system 100 in one embodimentof the present disclosure. As shown in FIG. 1, FIG. 2 and FIG. 3,whether the time period counted by the timer 1611 is greater than thepredetermined time is determined at operation 310. When the time periodcounted by the timer 1611 is less than or equal to the predeterminedtime, operation 320 is performed, where the PFC circuit 130 outputs thefirst voltage. Otherwise, operation 330 is performed, where the PFCcircuit 130 outputs the second voltage. A detailed description of theforegoing operations will be made below.

If we let t be the counted time period of the timer 1611 and t₁ be thepredetermined time, when t is less than or equal to t₁, the PFC circuit130 outputs the first voltage V₁, and when t is greater than t₁, the PFCcircuit 130 outputs the second voltage V₂. In the present embodiment,because the PFC circuit 130 outputs the first voltage V₁ with arelatively high voltage level during a time period that is within thepredetermined time t₁ (i.e., when t is less than or equal to t₁), theigniter 1410 is operated normally and the high ignition voltage isoutputted by the igniter 1410 to activate the discharge lamp 150.Preferably, the igniter 1410 continuously operates in a normal mannerduring this time period. When t is greater than t₁, the PFC circuit 130outputs the second voltage V₂ with a relatively low voltage level.During this time period, the igniter 1410 stops outputting the highignition voltage, that is, the igniter 1410 stops operating. Preferably,the igniter 1410 continuously stops working during this time period tothereby decrease the loss of the high ignition voltage for the dischargelamp 150, and as a result, the service life of the discharge lamp 150 isextended. Simultaneously, the PFC circuit 130 outputs the second voltageV₂ with the relatively low voltage level; therefore the efficiency ofthe whole discharge lamp system 100 can be improved.

Referring to FIG. 4A and FIG. 4B, controlling sequences will bedescribed that illustrate the discharge lamp system 100 in oneembodiment of the present disclosure. As shown in FIG. 1, FIG. 4A, andFIG. 4B, the controlling sequences are used for igniting a hot lamp (ornamely the discharge lamp 150), such that the output voltage of the PFCcircuit 130 shown in FIG. 1 can be controlled. As shown in FIG. 4A, atime period 0-t_(2n) can be made up of time periods T₁, T₂, . . . ,T_(n), where n is an arbitrary positive integer from 1 to N, and N is aninteger greater than 1, in which the time periods T₁, T₂, . . . , T_(n)can be the same or different. As shown in FIG. 4B, an initial timeperiod T₀ can be included before the time period T₁; that is, the timeperiod 0-t_(2n) is made up of the time periods T₀, T₁, . . . , T_(n), inwhich the time period T₁ is made up of Δt₁₁ and Δt₁₂ (or represented bythe time period from t₀ to t₂), and the time period T₂ is made up ofΔt₂₁ and Δt₂₂ (or represented by the time period from t₂ to t₄).Likewise, the time period T_(n) is made up of Δt_(n1) and Δt_(n2) (orrepresented by the time period from t_(2n-2) to t_(2n)), in which thetime periods T₀, T₁, . . . , T_(n) can be the same or different.

In this embodiment, the output voltages of the PFC circuit 130 can bethe first predetermined voltages V₁₁, V₂₁, . . . , V_(n1) during thetime periods Δt₁₁, Δt₂₁, . . . , Δt_(n1), respectively, in which theigniter 1410 can operate normally during the foregoing time periods,where the time periods Δt₁₁, Δt₂₁, . . . , Δt_(n1) can be the same ordifferent. Preferably, the first predetermined voltages V₁₁, V₂₁, . . ., V_(n1) can be equal, namely the PFC circuit 130 outputs the sameoutput voltage during the time periods Δt₁₁, Δt₂₁, . . . , Δt_(n1).Preferably, the igniter 1410 can operate normally during the timeperiods Δt₁₁, Δt₂₁, . . . , Δt_(n1). The output voltages of the PFCcircuit 130 can be the second predetermined voltages V₁₂, V₂₂, . . . ,V_(n2) during the time periods Δt₁₂, Δt₂₂, . . . , Δt_(n2),respectively, and the second predetermined voltages V₁₂, V₂₂, . . . ,V_(n2) are less than the corresponding first predetermined voltages V₁₁,V₂₁, . . . , V_(n1), in which the igniter 1410 stops operating duringthe foregoing time periods, where the time periods Δt₁₂, Δt₂₂, . . . ,Δt_(n2) can be the same or different. Preferably, the secondpredetermined voltages V₁₂, V₂₂, . . . , V_(n2) can be equal.Preferably, the output voltages of the PFC circuit 130 are equal duringthe time periods Δt₁₂, Δt₂₂, . . . , Δt_(n2). Preferably, the igniter1410 stops operating during the time periods Δt₁₂, Δt₂₂, . . . ,Δt_(n2).

The controlling sequences for the discharge lamp system 100 in thisembodiment provide for several advantages. Usually, a hot lamp needs asuper high voltage (about 20 kV) to ignite, and therefore, thecontrolling sequences can be used to lower the ignition voltage of thedischarge lamp 150, and the exhaust of the discharge lamp 150 can bedecreased. That is, the igniting process is performed during the timeperiods Δt₁₁, Δt₂₁, . . . , Δt_(n1), and when the discharge lamp 150 isunable to be activated, the igniting process can be aborted, after whichthe output voltage of the PFC circuit 130 is decreased to the secondpredetermined voltage. After the time periods for cooling down thedischarge lamp 150, such as Δt₁₂, Δt₂₂, . . . , Δt_(n2), re-ignition ofthe discharge lamp 150 is attempted. Namely, the output voltage of thePFC circuit 130 can be increased to the first predetermined voltage.Hence, the ignition voltage can be set to around 5 kV. Furthermore,after the time periods T₁, T₂, . . . , T_(n) of the time period 0-t_(2n)have elapsed, the output voltage of the PFC circuit 130 changes to thesecond predetermined voltage. In other words, the PFC circuit 130outputs the corresponding first predetermined voltage V₁₁ or V₂₁ . . .or V_(n1) during the first time period Δt₁₁ or Δt₂₁ . . . or Δt_(n1),during which the igniter 1410 operates normally. The PFC circuit 130outputs the corresponding second predetermined voltage V₁₂ or V₂₂ . . .or V_(n2) during the second time period Δt₁₂ or Δt₂₂ . . . or Δt_(n2),during which the igniter 1410 stops operating. The PFC circuit 130outputs a third voltage V₃ before the time t₀, where the value of thethird voltage V₃ is not limited to any specific value. After the timeperiods T₁, T₂, . . . , T_(n) of the time period 0-t_(2n) have elapsed,that is, after the time t_(2n), the PFC circuit 130 outputs the secondpredetermined voltage, and the igniter 1410 stops operating.

It is noted that the voltages V₁₁, V₂₁, . . . , V_(n1) can be equal orunequal as long as the requirement that the igniter 1410 can operatenormally during the time periods Δt₁₁, Δt₂₁, . . . , Δt_(n1) can besatisfied. Specifically, when the counted time period is within thefirst time period Δt_(i1) of the time period T_(i), the PFC circuit 130outputs the first predetermined voltage V_(i1), and when the countedtime period is within the first time period Δt_(j1) of the time periodT_(j), the PFC circuit 130 outputs the first predetermined voltageV_(j1), where i and j are integers from 1 to N, and i≠j. In the presentembodiment, the voltage V_(i1) can be equal to the voltage V_(j1). Inthe other embodiment of the present disclosure, the voltage V_(i1) canbe unequal to the voltage V_(j1); that is, V_(i1)≠V_(j1).

Similarly, the second predetermined voltages V₁₂, V₂₂, . . . , V_(n2)can be configured as the same voltage values or different voltagevalues. Specifically, when the counted time period is within the secondtime period Δt_(i2) of the time period T_(i), the PFC circuit 130outputs the second predetermined voltage V_(i2), and when the countedtime period is within the second time period Δt_(j2) of the time periodT_(j), the PFC circuit 130 outputs the second predetermined voltageV_(j2), where i and j are integers from 1 to N, and i≠j. In the presentembodiment, the voltage V_(i2) can be equal to the voltage V_(j2). Inthe other embodiment of the present disclosure, the voltage V_(i2) canbe unequal to the voltage V_(j2), that is V_(i2)≠V_(j2).

Referring to FIG. 5, a flow diagram will be described that illustrates acontrolling method for the controlling sequences shown in FIG. 4A. Asshown in FIG. 1, FIG. 4A, and FIG. 5, whether the counted time period isless than the time t_(2n) is determined at operation 510. When thecounted time period is less than the time t_(2n), whether the countedtime period is within the time period Δt_(n1) is determined at operation520. If so, operation 530 is performed. If not, operation 540 isperformed. At operation 530, the PFC circuit 130 outputs the firstpredetermined voltage V_(n1). At operation 540, whether the counted timeperiod is within the time period Δt_(n2) is determined. If so, operation550 is performed. If not, the routine returns back to operation 510. Atoperation 550, the PFC circuit 130 outputs the predetermined voltageV_(n2). If, at operation 510, the counted time period is not less thanthe time t_(2n), operation 560 is performed, that is, the PFC circuit130 outputs the second predetermined voltage as an arbitrary voltagevalue of the V_(n2) described above.

The present disclosure provides a technical solution for the dischargelamp system and the controlling method thereof. That is, the outputvoltage of the PFC circuit can be controlled by the time period countedby the timer, in order to control the open circuit voltage of thehalf-bridge inverter. Therefore the required voltage to ignite thedischarge lamp and to operate the same stably is provided, and thus asimple and efficient solution is provided. Moreover, because thehalf-bridge topology is adopted in the technical solution of the presentdisclosure, cost savings are realized.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims.

1. A discharge lamp system, comprising: an AC power source for providingan AC power; a rectifier for converting the AC power into a DC power; apower factor correction circuit electrically coupled to the rectifier,for generating an output voltage; a half-bridge circuit electricallycoupled to the power factor correction circuit and a discharge lamp, forconverting the output voltage into a voltage required by the dischargelamp; and a controller electrically coupled to the power factorcorrection circuit and the half-bridge circuit and comprising a timerfor counting time, wherein the controller is configured for controllingthe output voltage of the power factor correction circuit in accordancewith a time period counted by the timer.
 2. The discharge lamp system ofclaim 1, wherein the controller comprises: a controlling unit comprisingthe timer; a first driver for generating a first driving signal; and apower factor correction controller electrically coupled to thecontrolling unit and the first driver, for controlling the power factorcorrection circuit by the first driver in accordance with the timeperiod counted by the timer.
 3. The discharge lamp system of claim 2,wherein when the time period counted by the timer is less than or equalto a predetermined time, the power factor correction circuit outputs afirst voltage, and when the time period counted by the timer is greaterthan the predetermined time, the power factor correction circuit outputsa second voltage, wherein the second voltage is less than the firstvoltage.
 4. The discharge lamp system of claim 3, wherein thepredetermined time is greater than or equal to a required time to ignitethe discharge lamp.
 5. The discharge lamp system of claim 3, furthercomprising: an igniter activated when the time period counted by thetimer is within the predetermined time and deactivated when the timeperiod counted by the timer extends past the predetermined time.
 6. Thedischarge lamp system of claim 2, wherein the power factor correctioncircuit comprises a first switch, and the first driving signal isconfigured for driving the first switch.
 7. The discharge lamp system ofclaim 2, wherein the half-bridge circuit comprises a second switch and athird switch.
 8. The discharge lamp system of claim 7, wherein thecontroller further comprises: a second driver electrically coupled tothe controlling unit, for generating a second driving signal and a thirddriving signal, the second driving signal and the third driving signalbeing configured for driving the second switch the third switch,respectively.
 9. The discharge lamp system of claim 1, wherein thedischarge lamp is a high intensity discharge lamp.
 10. A controllingmethod for a discharge lamp system, comprising: determining whether atime period counted by a timer is greater than a predetermined time; andoutputting a first voltage by a power factor correction circuit when thetime period counted by the timer is not greater than the predeterminedtime, and otherwise, outputting a second voltage by the power factorcorrection circuit, wherein the second voltage is less than the firstvoltage.
 11. The controlling method of claim 10, wherein thepredetermined time is greater than or equal to a required time to ignitea discharge lamp.
 12. The controlling method of claim 10, wherein anigniter is activated when the time period counted by the timer is withinthe predetermined time and deactivated when the time period counted bythe timer extends past the predetermined time.
 13. A controlling methodfor a discharge lamp system, comprising: determining whether a countedtime period is within a time period T_(n) comprising a first time periodΔt_(n1) and a second time period Δt_(n2) following the first time periodΔt_(n1), wherein n is an arbitrary positive integer from 1 to N, and Nis an integer greater than 1; outputting a first predetermined voltageV_(n1) by a power factor correction circuit when the counted time periodis within the first time period Δt_(n1); and outputting a secondpredetermined voltage V_(n2) by the power factor correction circuit whenthe counted time period is within the second time period Δt_(n2),wherein V_(n2)<V_(n1).
 14. The controlling method of claim 13, furthercomprising: outputting the second predetermined voltage V_(n2) by thepower factor correction circuit when the counted time period is greaterthan time t_(2n).
 15. The controlling method of claim 13, furthercomprising: outputting a third predetermined voltage V₃ by the powerfactor correction circuit when the counted time period is less than timet₀.
 16. The controlling method of claim 13, further comprising:activating an igniter when the counted time period is within the firsttime period Δt_(n1); and deactivating the igniter when the counted timeperiod is within the second time period Δt_(n2).
 17. The controllingmethod of claim 13, further comprising: outputting the firstpredetermined voltage V_(i1) by the power factor correction circuit whenthe counted time period is within the first time period Δt_(i1) of thetime period T_(i); and outputting the first predetermined voltage V_(j1)by the power factor correction circuit when the counted time period iswithin the first time period Δt_(j1) of the time period T_(j); whereinV_(i1)≠V_(j1), i and j are integers from 1 to N, and i≠j.
 18. Thecontrolling method of claim 13, further comprising: outputting the firstpredetermined voltage V_(i1) by the power factor correction circuit whenthe counted time period is within the first time period Δt_(i1) of thetime period T_(i); and outputting the first predetermined voltage V_(j1)by the power factor correction circuit when the counted time period iswithin the first time period Δt_(j1) of the time period T_(j); whereinV_(i1)=V_(j1), i and j are integers from 1 to N, and i≠j.
 19. Thecontrolling method of claim 13, further comprising: outputting thesecond predetermined voltage V_(i2) by the power factor correctioncircuit when the counted time period is within the second time periodΔt_(i2) of the time period T_(i); and outputting the secondpredetermined voltage V_(j2) by the power factor correction circuit whenthe counted time period is within the second time period Δt_(j2) of thetime period T_(j); wherein V_(i2)≠V_(j2), i and j are integers from 1 toN, and i≠j.
 20. The controlling method of claim 13, further comprising:outputting the second predetermined voltage V_(i2) by the power factorcorrection circuit when the counted time period is within the secondtime period Δt_(i2) of the time period T_(i); and outputting the secondpredetermined voltage V_(j2) by the power factor correction circuit whenthe counted time period is within the second time period Δt_(j2) of thetime period T_(j); wherein V_(i2)=V_(j2), i and j are integers from 1 toN, and i≠j.